With the advent of using more electrically driven accessories on railcars, there becomes a need for providing self-contained electrical power systems on each railcar to drive the accessories.
It is known that railcars, and particularly freight cars, have begun to utilize electropneumatic braking systems responsive to electric and radio signals and that are significantly more efficient than the well known and standard pneumatic braking systems responsive to pneumatic command signals. The importance of electropneumatic braking systems is significant where long trains are made up for hauling freight. For example, some freight trains may have as many as 150 cars and extend for nearly two miles in length. Where such a train is dependent upon a pneumatic or air-driven braking system that responds to pneumatic signals from the locomotive, time delays are experienced in relaying those signals along the train. These time delays increase the amount of time needed to slow or stop a train of this magnitude and also impact on the maintenance requirements for the cars.
The development and operation of electropneumatic braking systems, such as disclosed in U.S. Pat. No. 5,722,736 and the PCT Publication No. WO 97/19844, require the use of electrical energy to drive the controller of the system. In these systems, each car includes its own electrically driven controller that responds to electric signals from the locomotive for operating the brake system of the car. It has been generally recognized that hard wiring along the train provides electrical energy for driving the controllers. This arrangement works particularly well if every railcar on the train is equipped with an electropneumatic braking system. Inasmuch as only a small number of railcars are presently equipped with electropneumatic braking systems, the advantage of using such a system on a train is at least partially lost where a train is made up with railcars having both electropneumatic and pneumatic braking systems which requires the electropneumatic systems to be responsive to pneumatic signals. A system responsive to either electric or pneumatic signals is referred to as an overlay or universal system. It should also be appreciated that railcars having only pneumatic braking systems are not fitted with wiring systems for passing electrical energy between railcars.
Therefore, a need is present for the use of self-contained power systems for railcars for not only driving controllers on electropneumatic braking systems but any other accessories such as signal lights at the end of the train.
Heretofore, it has been known to provide axle driven generators for land vehicles and even where those generators are driven by power taken from the wheels of the vehicle during movement of the vehicle. Such power generating systems are disclosed in U.S. Pat. Nos. 3,972,380; 4,021,690; 4,536,668; 4,539,497; 4,657,289; 4,761,577; 5,215,156; and 5,224,563.
It has been known to provide axle driven generators for railcars as disclosed in U.S. Pat. Nos. 723,727; 3,544,802; 4,071,282; 4,414,462; and 5,775,229. It has also been known to drive a hydraulic pump from a railcar axle that in turn drives a hydraulic motor that drives an alternator, as disclosed in U.S. Pat. No. 4,128,800. It has also been known that axle driven generators for railcars have been developed by Barrett Engineering, Inc. of San Diego, Calif., Ellcon National Inc. of Greenville, S.C., and The Timken Company.
Although the axle driven generators for railcars driven by the axles of a railcar produce a self-contained power generator, difficulties have been experienced not only in mounting the generators on a railcar but also maintaining them in satisfactory working operation. Accordingly, a need has been recognized for a self-contained power generating system that overcomes these problems.
While it has been proposed to drive air motor generators from brake pipe air or from supply reservoir air, such an arrangement would adversely affect brake application functions because the air capacity for operating a brake system would be reduced to the extent that braking capacity would be reduced to severely endanger the braking ability of the system. Moreover, air reductions of brake pipe pressure caused by exhausting brake pipe pressure to atmosphere through an air motor could create false pneumatic commands for the braking system, thereby causing malfunctioning of the system.